When I was in high school, my friends and I would sometimes chant “sleep is for the weak” when we wanted to get one more thing done or have a little more fun before the end of the day.

We just thought you went to sleep because it’s what adults told you to do. Of course, this isn’t true. In fact, NOT sleeping will MAKE you weak. Sleep is a foundation of your health, just like fitness and nutrition are. It affects every aspect of your health, from your mood to your memory to your immune system. Yet still, more than 87% of high school students in the United States don’t get the needed 8-10 hours of sleep.

Here are 8 amazing (and critical) things that sleep does for you. You need sleep to:

1. Feel alert

This might sounds like a “duh!” moment, but hear me out. Every system in your body consumes energy and produces waste, including the brain. This waste clogs the pathways that we need to think clearly, and is actually toxic to brain cells. Part of why you feel groggy when you’re tired is this waste building up in your brain.

When you sleep though, your brain’s sanitation department goes to work! These amazing cells clear out all the gunk your brain produces during the day, getting rid of that cloudy feeling. This helps you stay alert and pay attention during the day.

2. Learn new information

Sleeping helps your brain store memories and information, making them easier to retrieve later. This is partly why getting a good night’s rest before a big test is one of the best things you can do in order to boost your score!

Sleep is also when your brain “prunes” your neural connections. Pruning is when someone cuts away dying or dead parts of a plant, so that more water and minerals go to its healthy parts. Your brain does something similar when you sleep, pruning back connections that you no longer need. This lets your brain focus on the connections that you DO need.

3. Control your impulses and remain calm

Self-control can take a lot of mental energy. When you’re sleep deprived, you don’t have enough of this mental energy to regulate your emotions and keep yourself from doing things you wouldn’t normally do, like snapping at your friend, eating a second candy bar, or crying at something that normally wouldn’t upset you.

4. Keep you from getting sick

Your immune system, which keeps you from getting sick, relies on getting enough sleep to be able to function. When you’re sleep deprived, your immune system isn’t working quite like it needs to, making it more likely that you’ll get the common cold or another nasty bug floating around the school hallways.

5. Manage your metabolism

Not getting enough sleep messes with your metabolism, changing how your body processes energy.

In addition, lack of sleep can make you crave sugars and fats (and I’ve already mentioned how it weakens your ability to resist temptation). When you go to bed late, you’re also more likely to go for a midnight snack. Together, this means that not getting enough sleep can lead to weight gain, and long term sleep deprivation has been linked to metabolic illnesses like type 2 diabetes.

6. Help your mental health

Getting enough sleep is an important part of self-care, especially for people living with anxiety, depression or bipolar disorder. Without sleep these struggles can get harder. For those who are prone to psychotic or depressive episodes, not getting enough sleep can be a trigger. Sleep is an important tool for good mental health, just like therapy, medication, eating well and self-care.

7. Manage ADHD symptoms

The symptoms of sleep deprivation can mimic symptoms of ADHD because they both affect the same areas of the brain. This means that sleep is especially important for young people with ADHD, because their symptoms will actually get worse when they don’t get adequate sleep. Unfortunately, it is often harder for young people with ADHD to fall asleep in the first place. Because of this, one of the first things I do with new patients with ADHD is talk about a sleep routine.

You can learn more about how to get a good night’s sleep here.

8. Keep tabs on your mental, emotional and physical health

If you’re having trouble falling asleep, you may be dealing with stress, anxiety or depression. Pay attention to your thoughts at bedtime—WHY can’t you fall asleep? Is there something preoccupying your mind? Are you thinking about what you need to do tomorrow? That embarrassing thing you did two months ago? Paying attention to these thoughts can tell you about what your mind is preoccupied with, and give you some ideas for how you may be able to get a better night’s sleep.

Alternatively, do you all of a sudden not need as much sleep as you used to? Have you gone days without sleep and are still not tired? This can be a sign of another issue like mania.

Sleeping significantly more than you normally do may be a sign of depression or a medical concern like hypothyroidism.

Do you wake up after 8 hours and still not feel rested? You may have one of several medical conditions that can be treated, like sleep apnea, or a seizure disorder.

If you are struggling with not getting enough sleep, sleeping too much, or not feeling rested, talk to a health care provider.

They can help you with strategies for getting a good night’s rest, and make sure you aren’t dealing with a medical problem that needs attention. If you’re 10-22 years old in NYC, you can make a free appointment at Mount Sinai Adolescent Health Center with an adolescent medicine specialist or therapist.

Dr. Ariella Silver is an Assistant Professor in the departments of pediatrics and psychiatry at Mount Sinai Adolescent Health Center, and earned her doctorate in Clinical and School Psychology from Ferkauf Graduate School of Psychology in New York. She completed post-doctoral training at Mount Sinai’s Center of Excellence in ADHD and Related Disorders and the Seaver Autism Center for Research and Treatment. Dr. Silver’s areas of interest include, learning disorders, developmental disabilities, intellectual disabilities, autism spectrum disorder, anxiety, ADHD, and oppositional defiant disorder.

The Mount Sinai Adolescent Health Center is located in New York City. It provides comprehensive, confidential, integrated, judgment-free health care at no charge to over 12,000 young people every year. This column is not intended to provide medical advice, professional diagnosis, opinion, treatment or services to you or to any other individual, only general information for education purposes only.